Effect of uracil on pullulan production by Aureobasidium pullulans CGMCC1234

Effect of uracil on the pullulan production, biomass and uridine phosphorylase (UPase) activity was studied in this research. Uracil was found to enhance pullulan accumulation and the addition time of uracil was crucial to pullulan production. Pullulan yield of 49.07 g/L was achieved by adding 5 mM uracil at 48 h, by comparison to 37.72 g/L obtained with the control. UPase activity could not be detected at early growth stage of Aureobasidium pullulans, but stimulated by added uracil at logarithmic phase and stationary phase. The time course study on the fermentation of pullulan demonstrates that pullulan production was not closely associated with biomass accumulation. Results indicate that the increased pullulan yield brought by uracil was correlated with UPase activity.